In this chapter, fundamental processes in laser plasmas such as field ionization, laser propagation, classical laser absorption, and so on are described. When intense laser light irradiates a gas or solid target, plasmas are produced at the focus of the laser. Namely, field ionization takes place by laser interaction with the gas or solid surface and various laser plasma processes follow. Free electrons are heated by the laser and the electron impact ionization starts to produce hot dense plasmas. Electrons heated by the laser carry the energy to evaporate the solid surface which is called “laser ablation”. By evaporation of the solid, ablation plasmas called “corona plasmas” are produced. In laser interaction with the corona plasmas, various linear and nonlinear wave phenomena take place. We describe field ionization process, and plasma waves related to the laser plasma interactions. Then we describe the laser propagation and the collisional absorption in the corona plasmas. The collective absorption of laser and related wave phenomena are described in Chap. 11 .